Depletion models can predict shorebird distribution at different spatial scales

Predicting the impact of habitat change on populations requires an understa nding of the number of animals that a given area can support. Depletion mod els enable predictions of the numbers of individuals an area can support fr om prey density and predator searching efficiency and handling time. Deplet ion models have been successfully employed to predict patterns of abundance over small spatial scales, but most environmental change occurs over large spatial scales. We test the ability of depletion models to predict abundan ce at a range of scales with black-railed godwits; Limosa limosa islandica. From the type II functional response of godwits to their prey, we calculat ed the handling time and searching efficiency associated with these prey. T hese were incorporated in a depletion model, together with the density of a vailable pl ey determined from surveys, in order to predict godwit abundanc e. Tests of these predictions with Wetland Bird Survey data from the Britis h Trust for Ornithology showed significant correlations between predicted a nd observed densities at three scales: within mudflats, within estuaries an d between estuaries. Depiction models can thus be powerful tools for predic ting the population size that can be supported on sites at a range of scale s. This greatly enhances our confidence in predictions of the consequences of environmental change.